In the current version of RBM the raw damage of attack is calculated based on weapon type and skill of the attacker. The damage factor of weapon parts such as blades that is visible in the xml files (and probably crafting) represents sharpness / armor penetration of the weapon. Each weapon type have its own default armor penetration effectiveness.

For example one handed sword sword - it has these relevant stats: ExtraArmorThresholdFactorPierce = 3.5 and ExtraArmorThresholdFactorCut = 5; this means one point of armor can block 3.5 points of thrust damage from sword and 5 points of damage from cut. It is little bit more complicated than that because part of the blocked damage is turned into blunt trauma, etc but for the sake of this article these are the values that are relevant.

When sword has damage factor of 1 it means that it has 100% efficience in relation to the default value. The damage factor value is actually square rooted. So damage factor 1 = 2√1 = 1; damage factor of 1.2 = 2√1.2 = 1,095; damage factor of 0.8 = 2√0.8 = 0.894.

This final damage factor value is then used to divide the ExtraArmorThresholdFactor. So if raw damage of your sword swing is 100 this is how much armor will be sufficien to stop your strike depending on damage modifier (quality) of your weapon:

Be default 100 cutting damage from sword would be stopped by 20 armor because ExtraArmorThresholdFactorCut is 5 so 100 / 5 = 20.
Damage factor = 0.8; actual damage factor is 0.894; required armor to stop the hit = 100 / (5 / 0.894) = 100 / 5.592 = 17.88 armor is needed to stop the attack.
Damage factor = 1; actual damage factor is 1; required armor to stop the hit = 100 / (5 / 1) = 100 / 5 = 20 armor is needed to stop the attack.
Damage factor = 1.2; actual damage factor is 1.095; required armor to stop the hit = 100 / (5 / 1.095) = 100 / 5 = 21.96 armor is needed to stop the attack.

TLDR: melee weapon damage modifier 1 = default damage, less than 1 represents blutness, more than 1 represents sharpness.

Generally:
Tier 1 blades have damage modifier of 0.5-0.6
Tier 2 blades have damage modifier of 0.7-0.8
Tier 3 blades have damage modifier of 0.9
Tier 4 blades have damage modifier of 1-1.1
Tier 5 blades have damage modifier of 1.1-1.3

Specialized weapons might be on the higher end of the spectrum if they have only one type of damage. If blade has multiple types of attack but one type is preferred there should be some trade off, for example tier 3 sabre blade would have 1-1.05 cutting factor and 0.7 piercing factor because it is weapon specialized for cutting.

If you hower over weapon equipped in your character (or friendly hero) inventory it will show you its damage with the current character skill vs armor value of 0-100.